netShutdownPosix

fn netShutdownPosix(userdata: ?*anyopaque, handle: net.Socket.Handle, how: net.ShutdownHow) net.ShutdownError!void {
    if (!have_networking) return error.NetworkDown;
    const t: *Threaded = @ptrCast(@alignCast(userdata));
    _ = t;

    const posix_how: i32 = switch (how) {
        .recv => posix.SHUT.RD,
        .send => posix.SHUT.WR,
        .both => posix.SHUT.RDWR,
    };

    const syscall: Syscall = try .start();
    while (true) {
        switch (posix.errno(posix.system.shutdown(handle, posix_how))) {
            .SUCCESS => return syscall.finish(),
            .INTR => {
                try syscall.checkCancel();
                continue;
            },
            else => |e| {
                syscall.finish();
                switch (e) {
                    .BADF, .NOTSOCK, .INVAL => |err| return errnoBug(err),
                    .NOTCONN => return error.SocketUnconnected,
                    .NOBUFS => return error.SystemResources,
                    else => |err| return posix.unexpectedErrno(err),
                }
            },
        }
    }
}